Alpha-olefins, especially those containing about 6 to about 20 carbon atoms, are important items of commerce, with about 1.5 million tons reportedly being produced in 1992. Alpha-olefins are also used as intermediates in the manufacture of detergents, as monomers (especially in linear low density polyethylene), and as intermediates for many other types of products. As a consequence, improved methods of making these compounds are of value.
The dimerization of olefins by transition metal complexes represents an important class of industrially relevant chemistry.1 For example, ethylene dimerization to 1-butene can provide a source of comonomer in the production of polyethylene;2 and olefins such as propylene and butene are dimerized to give C6-C8 materials that serve as feedstocks for gasoline blending or alcohol production.3 
Most commercially produced alpha-olefins are made by the oligomerization of ethylene, catalyzed by various types of compounds, see for instance B. Elvers, et al., Ed. Ullmann's Encyclopedia of Industrial Chemistry, Vol. A13, VCH Verlagsgesellschaft mbH, Weinheim, 1989, p. 243-247 and 275-276, and B. Cornils, et al., Ed., Applied Homogeneous Catalysis with Organometallic Compounds, A Comprehensive Handbook, Vol. 1, VCH Verlagsgesellschaft mbH, Weinheim, 1996, p. 245-258. The major types of commercially used catalysts are alkylaluminum compounds, certain nickel-phosphine complexes, and a titanium halide with a Lewis acid such as diethylaluminum chloride (DEAC). In all of these processes significant amounts of branched and/or internal olefins and/or diolefins, are produced. Since in most instances these are undesired, and often difficult to separate from the desired linear alpha-olefins, minimization of these byproducts is sought.
In the field of olefin catalysis, tridentate iron catalysts are known for the production of α-olefins. Examples of these iron catalysts may be found in U.S. Pat. No. 6,103,946, issued Aug. 15, 2000, the disclosure of which is herein incorporated by reference.
Additional cobalt based catalysts useful for the oligomerization of propylene are taught in U.S. Pat. No. 6,063,881, the disclosure of which is herein incorporated by reference.
Currently, there are no known methods to selectively make linear internal olefins or alpha-olefins from propylene.
The development of cobalt catalysts having enhanced selectivity and high productivity in the production of olefins and alpha-olefins is of value.
Thus, it would be a significant contribution to the art to provide cobalt catalysts for the production of olefins which have both good productivity and high selectivity.